The overall objective of the proposed research program is a thorough understanding of the central nervous organization underlying the control of behavior. For this purpose, we are investigating the central nervous system of the marine gastropod, Tritonia, which offers considerable simplicity yet subserves a diverse repertoire of distinct, stereotyped behaviors. For the proposed project period, we will concentrate on an analysis of the organization and interactions of premotor interneurons and motor neurons to produce a motor output which is meaningful and useful to the animal. In particular, we are investigating the neuronal control of escape swimming, a highly organized and stereotyped behavior. We have three major aims for this proposed project. First is to describe and analyze mechanisms of pattern generation within the premotor interneuronal network. Secondly, we will quantitatively characterize the final motor output as recorded with multiple intracellular electrodes from central motor efferent neurons. This work includes analysis of single identifiable neurons both as individuals and as members of relatively large motor pools. Our third objective is to specify the projection and functional organization of premotor interneuronal output to the various efferent pools. We will concentrate on how the final motor output is derived by synaptic interconnections from the premotor interneurons. This work will provide new and valuable information of general interest on 1) mechanisms of pattern generation, 2) "rules" of motoneuron pool organization, and 3) the interaction of these two in determining motor output.